The invention relates to a method for treating the golf ball surface with unpolymerizable gas plasma so that the coating may be hard-exfoliative and an apparatus therefor.
There are provided various structure golf balls, which may be divided into two types. One type is the so-called thread-wound ball which comprises a core having a center which is a spherical bag filled with rubber latex etc. and rubber thread wound therearound, and an outer layer covering said core. The other type is the solid ball which comprises an inner layer or a plurality of layers of respectively different materials and an outer layer covering said inner layer(s).
Said outer layer of either type of balls is formed with various materials which may be gutta-percha, balata, a termoplastic elastomer and a so-called ionomer which is a metallic salt of copolymer of ethylene and an unsaturated carboxylic acid. The surface of such outer layer is formed with dimples of various numbers, sizes and patterns depending on ball makers in order to improve flight distance and stability, easiness for spin and the like, and in general carved with maker's trade mark and numerical figure for identification. The outer layer of the golf ball is further applied with coating such as paint and clear lacquer for the purposes not only of good appearance but also of improving flight distance and protecting said carved marks and figures.
Such coating is, however, often party exfoliated from the ball outer layer due to strong impact with a golf club, which naturally mars the ball appearance and adversely affects on the distance and stability of the ball flight.
In order to improve adhesive bonding between said outer surface and coating, some proposals have been made. One is the so-called flame method, according to which the ball surface is treated with a flame and then applied with coating. This is, however, unsatisfactory in that not only the effect is insufficient but also the ball material is often burned which may cause fire. Another countermeasure is to roughen the ball surface for instance by sand blasting and then apply the coating, which is also unsatisfactory in that precisely designed and formed dimples are damaged more or less to adversely affect on the ball flight and the purpose of improving the adhesive bonding of said two layers can not always satisfactorily be attained.
The technical problem of this field is, thus, to provide a method for considerably improving the adhesive bonding between the outer layer and coating of the golf ball so that coating is made hard-exfoliative without causing any other inconvenience as well as apparatus for effectively carrying out the method.